This graceful tree-dweller grows up to a length of 24 inches, including the long bushy tail. Tree squirrels do not have cheek pouches like ground squirrels but have the typical squirrel toe pattern - four toes on the front feet and five larger toes on the hind feet. The coat is overall gray above and white on the underside. The tail has white tips to the hairs.

The gray squirrel is primarily an acorn eater but feeds on various nuts and seeds and, in the spring, new leaf buds. The squirrel's den is in a tree cavity or in a nest of twigs, bark and leaves built far out on the branch of a large tree. It is seen foraging in trees or burying nuts in the ground during the day. It does no hibernate in the winter as do some ground squirrels.

Squirrels seen in parks in the Sacramento area are usually the imported eastern fox squirrel. These more aggressive immigrants tend to drive out native tree squirrels, demonstrating how the ecology of an area may be upset when new species are introduced.